1. Field of the Invention
The invention relates to a re-allocation method for a distributed Gateway GPRS Support Node (GGSN) system, which uses a GGSN controller to determine a GGSN re-allocation for a mobile station and performs the GGSN re-allocation by a GGSN or an SGSN corresponding to the mobile station, thereby enabling a GGSN system with dynamical load balancing and improving the system scalability.
2. Description of Related Art
GPRS networks are configured by packet switching based on the well-known GSM architecture. Accordingly, GPRS networks are compatible with GSM networks. Packet switching allows many people on-line to share network resources in a limited bandwidth. Further, encoding techniques have considerably improved, greatly increasing network data throughput. Thus, multimedia data transmission in a network is widely used.
FIG. 1 depicts an overall architecture of a typical GPRS network. In FIG. 1, the typical GPRS network belonging to Public Land Mobile Network (PLMN) includes a mobile station 100, multiple Base Station Subsystems (BSSs) 101, multiple SGSNs 102, a GGSN 103 and a host 104. In practice, the configuration can be varied as necessary, and is not limited to a mobile station 100, a GGSN 103 and a host 104. For the purpose of description, only a mobile station 100, a GGSN 103 and a host 104 are described.
As shown in FIG. 1, the mobile station 100 can access outside networks such as Internet or X.25 network via a path A passing through BSS 101, SGSN 102 and the GGSN 103. Each BSS 101 is responsible to control radio access and forwards data to GPRS core network. Each SGSN is in charge of relaying packets from radio networks to core network. Moreover, each SGSN handles mobility management (GMM) and session management (SM) in the GPRS network. For example, it handles different routing areas (RAs) and various mobiles' communication, including recording current mobile positions and completing packet accesses. The GGSN 103 serves as a gateway to access outside networks such as Internet or X.25 in order to send packets to a remote host such as the host 104. According to GPRS specifications, the initiation procedure of GPRS service includes powering on mobile stations and attaching powered-on mobile stations to the GPRS network. Attachment of a mobile station is to request a SGSN 102 to build up mobility management context in order to locate the mobile station. Once the mobile station has data to send or someone wants to send data to the mobile station, the mobile station will initiate or be asked to initiate a Packet Data Protocol (PDP) context activation. The PDP context activation asks the SGSN 102 to set up packet routing information on the SGSN 102 itself and the GGSN 103 so that the packets to/from the mobile station can be routed properly in the GPRS network. The PDP context information includes QoS profiles, access network information and corresponding GGSN IP addresses. The PDP context is released after the mobile station has deactivated its service. Based on design philosophy, GGSN selection is only performed at activation time. For example, when the mobile station 100 activates services and then starts its packet delivery/receiving, operators of the GPRS system can assign a GGSN 103 with the lowest load to the mobile station 100 based on Access Point Network (APN) or other GGSN selection policies. The assigned GGSN 103 is permanent once the GGSN 103 is assigned to the mobile station 100 until the PDP context of the mobile station 100 is deactivated. Therefore, all services to the mobile station 100 are completed by the GGSN 103. In practice, packet data is delivered in bursts For example, the operator may assign the same number of mobile stations to two GGSNs 103. As more and more subscribers request packet service in GPRS or future telecommunication networks, it becomes necessary to allocate a pool of GGSNs in PLMN to serve users. However, due to the permanent relation of a mobile station to an assigned GGSN and in practice, packet data is delivered in bursts, GGSNs cannot perform load balance even the number of serving MSs are the same. Therefore, in the typical GPRS network, one or more of GGSNs 103 may create a bottleneck.